Download Chapter 2: The Physical Environment

Bio 122 S13 KLB
Lecture 1: Ecology Intro; Climate
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Chapter 2: The Physical Environment
Habitability – the ability of a physical environment to support life
Climate
Climate = long-term average pattern of weather in an area
weather = combination of temperature, precipitation, wind, cloudiness occurring at a
specific time and place
Solar radiation
 about half (~49%) of the solar energy that strikes the atmosphere is either absorbed or
reflected by the atm and clouds and sent back to space
 about half (~51%) of the solar radiation striking the earth's atmosphere successfully
penetrates the atmosphere to reach earth.
~45% evaporate water
~14% warms the air next to the earth’s surface
~41% absorbed by land masses and oceans
 Land and oceans reflect radiation (=heat=energy) back into the atmosphere
 ~6% of the reflected energy passes through & back into space
 the rest is absorbed by water vapor & CO2 in atm most of which is then radiated
back to earth producing the greenhouse effect
Temperature - varies due to tilt of the earth on its axis
Latitude
 less radiation strikes at high latitudes than the equator
→ creates a gradient of decreasing temp as you move from the equator to the poles
Season
 Earth’s tilt in combination with its orbit around the sun causes seasons
 Seasons reflect differences in the amount of solar radiation hitting the same point at
different times of the year
Altitude
 As one moves up in altitude, temperatures decrease
1. air pressure declines with altitude
 air under lower pressure moves more slowly
 temperature is a measure of how fast air molecules are moving, where faster
= warmer; slower = cooler
2. decline in “warming effect”
 absorption of solar energy warms the surface of the earth
 as you move upward, the energy dissipates and the temperature declines
Bio 122 S13 KLB
Lecture 1: Ecology Intro; Climate
Global Circulation
a) Air masses
Atmosphere = Blanket of air surrounding earth; this air mass is in a constant state
of motion
Air circulation caused by:
1. rising & sinking air masses
2. earth’s rotation around axis
o Coriolis effect
combination of vertical and horizontal movement creates a series of belts of
prevailing winds.
b) Ocean currents
 Atm circulation pushes water in the same direction as prevailing winds
 Water influenced by Coriolis effect,
Precipitation
 Patterns of air circulation create areas of rising wet, warm air and falling cool, dry air
1) Warm, high levels of precipitation → Tropics
2) Relatively warm & arid → Subtropical &Temperate regions
3) Cool, high levels of precipitation → just below polar area; coniferous forests
4) Cold, arid → polar regions (Arctic and Antarctic)
Summary animation:
http://www.kevinflint.org/ppt/chap5/Animations/global_circ_anim.html
Microclimates
 large scale global patterns set up the 1st order of distribution of organisms, but local
conditions define the actual environmental conditions a given organism experiences
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